Extensible absorbent articles such as sanitary napkins, panty liners, and incontinence pads are known (see, e.g., patent literature 1). The absorbent article according to patent literature 1 is characterized by having flexibility and capability of extending and contracting together with an undergarment.
Extensible absorbent members are also known (see, e.g., patent literature 2). The absorbent member of patent literature 2 has two extensible layers woven of elastic threads and a number of material bodies arranged in two dimensions between the layers, the material bodies being made of a superabsorbent material and fibrous fluff.    [Patent literature 1] WO96/10974    [Patent literature 2] WO91/09581
The absorbent article of patent literature 1 is designed to extend together with an undergarment to which it is attached but not be extended as much as a user wants when the user attaches it to the undergarment. In other words, the article is not designed to be used as extended to a size appropriate to the anatomy of an individual wearer's body. Nor it is given a device to prevent reduction of absorbency when it is extended.
The absorbent member of patent literature 2 generates gaps between the material bodies participating in absorption when it is extended. Therefore, the extended absorbent member will have lower absorbency than before being extended because liquid passes through the gaps.